| Vertical fall. | Vertical rebound. | Duration of contact. | ||
| inch. | inch. | seconds. | ||
| 1 | 3⁄4 | 0 | 1⁄3 | 0.00036 |
| 6 | 1 | 0.00033 | ||
| 14 | 1⁄2 | 1 | 1⁄2 | 0.00026 |
| 25 | 2 | 0.00027 | ||
This series also shows the longer duration of the blow when its velocity is small. Using a brass anvil and iron ball the duration of the blow was greater than when both were of iron, but less than when both were of brass.
| Vertical fall. | Vertical rebound. | Duration of contact. | ||
| inch. | inch. | seconds. | ||
| 1 | 3⁄4 | 0 | 1⁄8 | 0.00021 |
| 6 | 0 | 1⁄2 | 0.00018 | |
| 14 | 1⁄2 | 1 | 1⁄3 | 0.00015 |
| 25 | 2 | 0.00014 | ||
Striking the brass anvil with a common hammer, the duration of the blow appeared shorter when struck sharply.
| Duration of contact. | |
| seconds. | |
| Moderate blow | 0.00027 |
| Harder blow | 0.00019 |
Striking the blacksmith’s anvil with a common carpenter’s hammer, the duration appeared to be nearly constant.
| Duration of contact. | |
| seconds. | |
| Moderate blow | 0.00011 |
| Harder blow | 0.00010 |
It was, of course, necessary to allow in each case the hammer to rebound freely, and not to prevent it doing so by continuing to exert any pressure at the instant of the blow. When this condition was observed, it was invariably found that the harder and sharper the blow the shorter was its duration. It was also noticed that whenever the anvil gave out a sharp ringing sound, the duration of the blow was much shorter than when the sound was dull.
A very slight error would be introduced by reason of thermo-currents set up between the metals at the moment of the blow. By reversing the direction of charge of the accumulator, however, the effect from this cause was found to be quite inappreciable.